1. Field of the Invention
This invention relates to concrete curing blankets, and it more particularly relates to these blankets formed by reinforced plastic sheets.
2. Background of the Invention
One of the requirements to produce quality concrete is its proper manipulation during curing. The curing process produces chemical changes timewise that relate to setting and hardening, and they continue to occur over a considerable period of time in the presence of water. Thus, concrete must be kept wet after it has set for as long a period as is practicable. Curing not only increases the strength of concrete and its structural value, but proper curing is necessary for the production of water-tight and durable concrete.
For example, if concrete is kept wet for the first ten days after setting, its strength and durability increase 75 percent over ordinary aging at dry surface conditions. Thus, concrete structures should be cured by adequate means. These means include drenching the forms etc. with water prior to pouring. Then, the concrete surface is kept damp by frequent sprinklings, but this means is labor intensive and expensive.
Horizontal surfaces of concrete have been covered by sand or canvas or burlap to maintain the desired dampness to promote curing. However, irregular concrete surfaces, such as steps, bridge columns, decks or walls cannot be covered but have had to be sprinkled periodically for the necessary damp condition.
It has been proposed to use concrete curing blankets to cover water-wetted concrete and thereby extend the duration of the damp condition. One blanket was formed of coarse, woven burlap fibers which were carried a thermoplastic sheet that was heat sealed or melted onto the fabric. Naturally, the burlap is hydrophillically greasy, subject to rotting, and the water wetting the concrete in part was absorbed by these natural fibers. Also, large void areas were present in the burlap weave which promote non-uniform wetting of the concrete surface, especially if it is irregular or non-horizontal. The blanket is relatively stiff and unyielding and thus, it tends not to conform to surface irregularity. If the blanket is slid upon irregular concrete, the burlap fibers snag and hang to make placement difficult, and sometimes even causing the tearing of the blanket. After use, the blanket with burlap fibers could not be merely rolled and stored because of the bacterial action on the natural fibers which could even lead to spontaneous combustion hazards. Air or artifically drying the blanket so it can be reused is not only inconvenient but relatively expensive.
The present concrete curing blanket is light weight, maintains uniform wetness against the concrete and conforms to irregular surfaces, and it is not subject to bacterial degradation. It is readily joined between adjacent pieces by heat sealing to cover large concrete surfaces. Also, it can be rolled wet for transportation to the next site for curing concrete.